Applications

For the most part, applications that take advantage of the material properties of nanometer-scale multiple-layer films are still in the development stage. Within the past few years, however, a number of promising applications have emerged that seem especially well suited for multiple-layer alloy plating.

The magnetic properties of electroplated multiple-layer alloys have received a great deal of attention for applications related to magnetic recording. For example, Ref 1 shows that multiple-layer thin films of Cu/Ni-Fe (^Cu »10 nm and ^Ni.Fe » 50 nm) eliminate the classical edge-closure domains that give rise to noise in thin-film inductive heads. At the same time, the remaining magnetic properties of the multiple-layer Cu/Ni-Fe alloy are comparable to homogeneous Ni-Fe alloy properties. The combination of reduced domain noise in the multiple-layer alloy with excellent magnetic properties makes these materials extremely attractive for thin-film inductive heads with very narrow track width. It is also likely that electroplated multiple-layer alloys will soon affect the performance of magnetoresistive head technology, given the recent discovery of giant magnetoresistance in electroplated Cu/Co-Ni-Cu multiple-layer alloys with ^Cu <1 nm (Ref 2).

Electroplated multiple-layer foils of Ni/Cu alloy (with ^Cu » 2 nm and XNi »18 nm) exhibit tensile strengths that exceed homogeneous nickel or copper foil strengths by more than a factor of three (Ref 3), and steel that is coated with an electroplated Ni/Cu multiple-layer film (^Cu » 3.8 nm and XNi » 3.8 nm) exhibits a high resistance to sliding wear (Ref 4). Because of these enhanced mechanical properties, electroplated Ni/Cu multiple-layer surface coatings are being used to extend the lifetime of printing press components that are subject to sliding-wear damage.

Other applications of electroplated multiple-layer thin films that are being explored include the use of Cu/Ag and Cu/Co alloys for high-temperature applications in rocket thrust aligners, where protective surface films are used to minimize hydrogen embrittlement.

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